The careful examination of the chain by members of the English and French Alpine Clubs has since 1880 considerably modified the views held with respect to its general character; the southern versant, formerly regarded as inferior in, area, has been proved to be the more important of the two.
The importance shown to attach to the Spanish versant has greatly modified the values formerly assigned to the area and mean elevation of the Pyrenees.
The Kebbi, fed by many torrents rising in the eastern versant of the Mandara Hills, issues from the S.W.
In some places limestones appear as projections from the range; at others conglomerates and Tertiary clay marls form the outermost fold."' On the north versant of the ranges the rainfall increases from the foot of the mountains upwards, and at woo-10,000 ft.
The south versant, on the other hand, is barren and desolate below the 10,000 ft.